In recent years, there has been a heightened sense of awareness concerning the need to clean and maintain the environment from contaminants. It has become of paramount importance to clean-up areas of soil that have been exposed to contamination. A number of methods have developed in treating the soil to rid such soil of contaminants, but each method has had definable disadvantages.
One reoccurring problem in soil remediation has been the cost of constructing and maintaining equipment used to decontaminate the soil. Although the methods for clean-up are relatively simple, the equipment used to employ these methods has been traditionally complex and expensive. Accordingly, it is desired that a means for soil remediation be achieved through the most inexpensive and reliable means possible.
For in situ treatment of contaminated soil, common means for remediation require the drilling of numerous wells. Typically, an injection well is accompanied by a separate extraction well for remediation means such as air stripping or vacuum extraction. Some decontamination methods utilize only one well, however, this mono-well concept has previously required complex designs and an exhaustive array of materials.
From the foregoing, it can be seen that a need exists for a technique to decontaminate soil in which a minimum amount of materials and labor are needed. While the prior art may be effective for its intended purpose, such prior art does not present simple yet efficient means for remediation.
For example, U.S. Pat. No. 5,221,159 to Billings et al. is directed to a method and apparatus for removing contaminants from soil and an associated subsurface ground water aquifer. This invention requires two wells, namely, an injection well and adjacent extraction wells that are drilled to a depth above the water table. Oxygenated gas is injected through the injection well while a vacuum is applied to the extraction well. Contaminants are removed from the ground water aquifer and from the vadose zone by a combination of physical, chemical and biochemical processes. Relatively pure liquid contaminant may be extracted simultaneously with cleansing of the soil above the aquifer. Microbes natural to the contaminated site are extracted, analyzed, fermented and reintroduced into the soil to enhance biodegration.
U.S. Pat. No. 5,180,503 to Gorelick et al. is directed to an in-situ method and apparatus for removing volatile organic compounds from ground water. The technique includes gas-lift pumping and in-situ vapor stripping. The apparatus includes means for injecting a gas into a well to force ground water flow towards the well and to cause volatile compounds to be transferred from the ground water to rising gas bubbles inside the well. The apparatus further includes means at the top of the well for collecting vapor contained within the gas bubbles. Injection of air is provided through an air line below the water table to a saturated zone containing the contaminants. The contaminants are drawn in through a well screen and rise through a well casing which surrounds the air line.
U.S. Pat. No. 5,032,042 to Schuring et al. discloses a system for eliminating contaminants from the soil and creating a fracturing assembly for pneumatically fracturing the soil. The fracturing assembly includes a probe which is inserted into a well and which receives pressurized gas. First and second packers press against the well so as to provide a sealed area in the well. Pressurized gas is applied through a nozzle including at least one orifice therein. Fracturing of the soil allows for conductive channels to be created which permits more rapid movement of contaminants through the soil. The pressurized gas travels through the fractures created in the soil and a transformation means is provided such that liquid toxic contaminants in the soil are vaporized.
U.S. Pat. No. 5,011,329 to Nelson et al. is directed to a method and apparatus for in-situ decontamination of soil. Hot gas is injected into bore holes formed in a contaminated soil area to vaporize the soil moisture and contaminants, and for collecting the vaporized contaminants at the surface of the soil. A burner heats pressurized gases and mixes the same with the combustion gases for injection into the contaminated zone. A central collection system recovers the vaporized contaminants and couples such vapors to an on-site incinerator for disposal.
U.S. Pat. No. 4,711,306 to Bobo is directed to a method for decontaminating soil wherein a gas lift system is used. Pressurized injection gas is mixed with pressurized injection liquid prior to introducing the pressurized mixture into a bore hole. The pressurized injection gas and liquid mixture is introduced into one portion of the well bore to a point below an initial column of well fluid present in another portion of the well bore conduit. As the mixture of injection gas and liquid travels toward the bottom of the well bore, the gas is compressed increasingly by the height of the column of liquid thereabove and is subsequently passed to another portion of the well bore where the gas rises and expands to lift oil or other contaminant fluids to the surface.
U.S. Pat. No. 4,886,119 to Bernhardt et al. is directed to a method for driving volatile impurities from the ground wherein a bore hole is provided with a central shaft whose upper end is sealed from the outside by a plate. A first non-perforated suction pipe extends in the drilling shaft to the proximate end of the shaft. A second suction pipe concentrically surrounds the first suction pipe, with a space therebetween, and extends to half the length of the drilling shaft. The inner ends of both pipes form suction locations. The ends of the suction pipes extend outside of the shaft in a fluid separating chamber. Means for drawing a vacuum is provided at the upper end of the drilling shaft. Sieve ring bodies are arranged at the ends of the suction pipes, each of which has a flexible sieve wall which can be composed of metal sieve web or synthetic plastic sieve web. The upper part of the shaft is supported by loose aggregate material.
While each of the inventions described above fulfills its intended purpose, each structure is somewhat complex and therefore expensive to provide and requires significant labor for installation. Another disadvantage of these inventions is that the injection fluid cannot be selectively placed in the desired area of the soil without either changing the depth of the well or position of the injection tube.